This application claims priority on Japanese Patent Application No. 11-320202 filed on Nov. 10, 1999, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a battery pack containing a plurality of cells for use with a charger or battery-powered devices, such as power tools, as a power source. More particularly, the invention relates to a battery pack with an improved structure for cooling the cells during a charge.
2. Description of the Related Art
A conventional battery pack includes on the top surface thereof a mounting portion which in turn includes electrical terminals for the establishment of electric contact between the battery pack and a charger or a battery-powered device, such as an electric power tool. The battery pack can be recharged by attachment of its mounting portion onto the charger, and also can be used as a power source by attachment of the mounting portion onto a battery-powered device. However, the cells of the battery pack tend to generate heat during each charge, which results in degradation of the cells. To avoid such a disadvantage, a means for cooling the battery cells is typically provided in the battery pack. For example, disclosed in Japan Published Unexamined Patent Application No. 11-219733 is a battery pack which is provided with a cooling structure therein. The structure includes air passages running through the battery pack case and along and between the cells within the battery pack and a plurality of apertures forming intake and discharge ports provided at the top and bottom portions of the battery pack, whereby the intake ports are disposed at a mounting portion to which a charger is attached, with the air passages in communication with both the intake and discharge ports. Thus, cooling air from a blower or fan incorporated in the charger can be introduced from the intake ports to be sent into the interior of the pack through the air passages and outside the pack from the discharge ports so that the heat generated by the cells during a charge is dissipated therefrom.
While the foregoing battery pack with a cooling structure for the battery cells contained therein achieves its intended objective, it is not free from certain problems and inconveniences, thus leaving room for improvement. For example, in the above described structure, foreign substances such as dust and other various types of debris can easily enter the interior of the battery pack, as the discharge ports, which are provided at the bottom of the battery pack and are in communication with the air passages, are exposed in an upward direction to the external environment when the battery pack is mounted onto the charger for a charge. If such substances are electrically conductive, this may result in occurrence of a short circuit in the battery pack. Also, when the battery pack is mounted onto battery-powered tools, not only debris but even rain drops may enter the battery pack if such tools are used in environments in which the tool is exposed to rain, since the pack""s bottom surface where the discharge ports are located is exposed to the exterior environment. This also may cause rust, corrosion, or liquid electrolyte leakage of the cells.
In view of the above-identified problems, a primary object of the present invention is to provide a battery pack for use with a charger or battery-powered devices which can eliminate the possible causes of the above-identified problems by prevention of foreign substances from intruding into the battery pack when the battery pack is mounted onto a charger or battery-powered devices without reducing the effect of cooling the cells during each charge.
The above objects and other related objects are realized by the invention, which provides a battery pack including: an outer enclosure containing a plurality of battery cells and having a mounting portion adapted to be removably attached to a charger and other electric devices; at least one intake port provided in the mounting portion for introducing into the battery pack cooling air supplied from a charger; and at least one discharge port provided in the mounting portion for discharging the cooling air from the battery pack. The battery pack further includes at least one air passage connecting the at least one intake port to the at least one discharge port such that the at least one air passage allows the cooling air introduced through the at least one intake port to flow along and/or between the cells and to be discharged through the at least one discharge port. As the at least one intake port and the at least one discharge port of the air passage are both provided at the mounting portion of the battery pack, neither port is exposed to the exterior of the battery pack when the pack is mounted on a charger or another electric device. This structure prevents foreign substances such as water, dust and other various types of debris from entering the interior of the battery pack, such that rust, corrosion, or liquid electrolyte leakage of the cells which may otherwise be caused by ingression of such foreign substances do not occur.
According to one aspect of the present invention, the mounting portion includes a substantially rectangular top plate having a first edge and an opposite second edge, with the at least one intake port being formed on the top plate in proximity to the first edge and the at least one discharge port being formed in proximity to the second edge.
According to another aspect of the present invention, the mounting portion is contoured to generally correspond to a connecting portion of the charger and those of the aforementioned other electric devices such that, when the battery pack is attached to any of the charger and the aforementioned other electric devices, the at least one intake port and the at least one discharge port are unexposed to the exterior environment of the battery pack and the electric device to which the battery pack is currently attached.
According to still another aspect of the present invention, when the battery pack is attached to the charger, a narrow gap is formed at least along the second edge of the top plate between the mounting portion of the battery pack and the connecting portion of the charger so as to facilitate discharge of cooling air from the at least one discharge port.
According to yet another aspect of the present invention, the mounting portion includes a step along the second edge where the at least one discharge port are provided, the step forming the narrow gap with the connecting portion of the charger.
According to one feature of the present invention, the battery pack further includes an inner case holding the cells and includes a plurality of radiators in contact with the cells, and the at least one air passages are separated from the cells by the inner case. As the radiator plates, which are brought into contact with the battery cells, are included on the inner case, the dustproof effect for the cells is further enhanced without reducing the effect of cooling the cells.
According to another feature of the present invention, each radiator is a radiator plate having a plurality of fins protruding into the air passage and oriented substantially in parallel to the direction of the flow of cooling air introduced through the at least intake port.
According to still another feature of the present invention, the number of fins of each radiator plate increases in the downstream direction of the cooling airflow.
According to yet another feature of the present invention, the battery pack includes a pair of slide rails on the mounting portion and each of the charger and the electric devices includes on the connecting portion thereof a pair of guide rails which can slidably engage the slide rails such that the battery pack is attached to the charger and the electric devices by slide motion.
According to one practice of the present invention, the plurality of cells are divided into two groups by a longitudinal gap formed through the inner case, and one of the air passages is at least partially defined by the gap between the two cell groups.
According to another practice of the present invention, the outer enclosure includes two inner longitudinal walls and the inner case includes two outer longitudinal walls which opposes the inner longitudinal walls across a selected distance so as to at least partially define two of the air passages between the outer longitudinal walls and the inner longitudinal walls.
According to still another practice of the present invention, the electric devices include electric power tools.
According to yet another practice of the present invention, the charger includes a housing, at least one inlet port provided in the housing, and at least one exhaust port provided in the housing. When the battery pack is set on the charger for charging, the at least one inlet port is located in the portion of the housing directly opposing the at least one discharge of the battery pack so as to allow the cooling air discharged out of the discharge ports of the battery pack to reenter the charger through the inlet port and to be discharged from the charger through the exhaust port.
The invention is also directed to a battery pack charging system comprising a battery pack and a charger on which the battery pack is set for charging. The battery pack includes: an outer enclosure containing a plurality of battery cells and having a mounting portion adapted to be removably attached to the charger and other electric devices; at least one intake port provided in the mounting portion for introducing cooling air into the battery pack from the charger; at least one discharge port provided in the mounting portion for discharging the cooling air from the battery pack; and at least one air passage connecting the at least one intake port to the at least one discharge port, with the at least one air passage allowing the cooling air introduced through the at least one intake port to flow along and/or between the cells and to be discharged through the at least one discharge port. The charger includes: a housing having a connecting portion to which the mounting portion of the battery pack is attached for charging; a fan contained within the housing for supplying cooling air to the battery pack; and at least one airflow passage port formed in the connecting portion for directing the cooling air supplied from the fan into the intake port of the battery pack when the battery pack is set on the charger.
In one embodiment, the charger further includes: at least one inlet port formed in the portion of the connecting portion opposing the at least one discharge when the battery pack is set on the charger; and at least one exhaust port formed in the connecting portion and placed in pneumatic communication with the at least one inlet port. In this embodiment, at least part of the cooling air discharged from the discharge port of the battery pack is allowed to reenter the charger through the inlet port and to exit from the charger through the exhaust port.
Other general and more specific objects of the invention will in part be obvious and will in part be evident from the drawings and descriptions which follow.